Ducted fan VTOL vehicles

ABSTRACT

A vehicle including a fuselage having a longitudinal axis and a transverse axis, two Ducted Fan lift-producing propellers carried by the fuselage on each side of the transverse axis, a pilot&#39;s compartment formed in the fuselage between the lift-producing propellers and substantially aligned with one side of the fuselage, a payload bay formed in the fuselage between the lift-producing propellers and opposite the pilot&#39;s compartment, and two pusher fans located at the rear of the vehicle. Many variations are described enabling the vehicle to be used not only as a VTOL vehicle, but also as a multi-function utility vehicle for performing many diverse functions including hovercraft and ATV functions. Also described is an Unmanned version of the vehicle. Also described are unique features applicable in any single or multiple ducted fans and VTOL vehicles.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application is a continuation of U.S. patent application Ser. No.11/411,243 filed Apr. 26, 2006, which is a continuation-in-part of PCTApplication PCT/IL2004/000984 filed Oct. 27, 2004, claiming priorityfrom U.S. Provisional Patent Application Nos. 60/514,555, filed Oct. 27,2003 and 60/603,274, filed Aug. 23, 2004. Priority is also claimed fromU.S. Provisional Patent Application No. 60/731,924 filed Nov. 1, 2005.The entire subject matter of all of the above is incorporated byreference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to vehicles, and particularly to VerticalTake-Off and Landing (VTOL) vehicles having multi-function capabilities.

VTOL vehicles rely on direct thrust from propellers or rotors, directeddownwardly, for obtaining lift necessary to support the vehicle in theair. Many different types of VTOL vehicles have been proposed where theweight of the vehicle in hover is carried directly by rotors orpropellers, with the axis of rotation perpendicular to the ground. Onewell known vehicle of this type is the conventional helicopter whichincludes a large rotor mounted above the vehicle fuselage. Other typesof vehicles rely on a multitude of propellers that are either exposed(e.g., unducted fans), or installed inside circular cavities, shrouds,ducts or other types of nacelle (e.g., ducted fans), where the flow ofair takes place inside ducts. Some VTOL vehicles (such as the V-22) usepropellers having their axes of rotation fully rotatable (up to 90degrees or so) with respect to the body of the vehicle; these vehiclesnormally have the propeller axis perpendicular to the ground forvertical takeoff and landing, and then tilt the propeller axis forwardfor normal flight. Other vehicles use propellers having nearlyhorizontal axes, but include aerodynamic deflectors installed behind thepropeller which deflect all or part of the flow downwardly to createdirect upward lift.

A number of VTOL vehicles have been proposed in the past where two orfour propellers, usually mounted inside ducts (i.e., ducted fans), wereplaced forwardly of, and rearwardly of, the main payload of the vehicle.One typical example is the Piasecki VZ-8 ‘Flying Jeep’ which had twolarge ducts, with the pilots located to the sides of the vehicle, in thecentral area between the ducts. A similar configuration was used on theChrysler VZ-6 and on the CityHawk flying car. Also the Bensen ‘FlyingBench’ uses a similar arrangement. The Curtiss Wright VZ-7 and theMoller Skycar use four, instead of two, thrusters where two are locatedon each side (forward and rear) of the pilots and the payload, thelatter being of fixed nature at the center of the vehicle, close to thevehicle's center of gravity.

The foregoing existing vehicles are generally designed for specificfunctions and are therefore not conveniently capable of performing amultiplicity of functions.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a vehicle of arelatively simple inexpensive construction and yet capable of performinga multiplicity of different functions.

According to the present invention, there is provided a vehicle,comprising: a fuselage having a longitudinal axis and a transverse axis;at least one lift-producing propeller carried by the fuselage on eachside of the transverse axis; a pilot's compartment formed in thefuselage between the lift-producing propellers and substantially alignedwith the longitudinal axis; and a pair of payload bays formed in thefuselage between the lift-producing propellers and on opposite sides ofthe pilot's compartment.

According to further features in the preferred embodiments of theinvention described below, each of the payload bays includes a coverdeployable to an open position providing access to the payload bay, andto a closed position covering the payload bay. In some describedpreferred embodiments, the cover of each of the payload bays ispivotally mounted to the fuselage along an axis parallel to thelongitudinal axis of the fuselage at the bottom of the respectivepayload bay, such that when the cover is pivoted to the open position italso serves as a support for supporting the payload or a part thereof inthe respective payload bay.

Various embodiments of the invention are described below, wherein thelift propellers are ducted or unducted fans, and wherein the fuselagecarries a pair of the lift producing propellers on each side of thetransverse axis, a vertical stabilizer at the rear end of the fuselage,or a horizontal stabilizer at the rear end of the fuselage.

Several preferred embodiments are also described below wherein thefuselage further carries a pair of pusher propellers at the rear end ofthe fuselage, on opposite sides of the longitudinal axis. In thedescribed embodiments, the fuselage carries two engines, each fordriving one of the lift-producing propellers and pusher propellers withthe two engines being mechanically coupled together in a commontransmission. In one described preferred embodiment, the two engines arelocated in engine compartments in pylons formed in the fuselage onopposite sides of its longitudinal axis. In another describedembodiment, the two engines are located in a common engine compartmentaligned with the longitudinal axis of the fuselage and underlying thepilot's compartment.

One preferred embodiment is described wherein the vehicle is a verticaltake-off and landing (VTOL) vehicle and includes a pair of stub wingseach pivotally mounted under one of the payload bays to a retracted,stored position, and to an extended, deployed position for enhancinglift. Another embodiment is described wherein the vehicle includes aflexible skirt extending below the fuselage enabling the vehicle to beused as, or converted to, a hovercraft for movement over ground orwater. A further embodiment is described wherein the vehicle includeslarge wheels attachable to the rear end of the fuselage for convertingthe vehicle to an all terrain vehicle (ATV).

As will be described more particularly below, a vehicle constructed inaccordance with the foregoing features may be of a relatively simple andinexpensive construction capable of conveniently performing a host ofdifferent functions besides the normal functions of a VTOL vehicle.Thus, the foregoing features enable the vehicle to be constructed as autility vehicle for a large array of tasks including serving as aweapons platform; transporting personnel, weapons, and/or cargo;evacuating medically wounded, etc., without requiring major changes inthe basic structure of the vehicle when transferring from one task toanother.

According to further features in the preferred embodiments of theinvention described below an alternative vehicle arrangement isdescribed wherein the vehicle is relatively small in size, havinginsufficient room for installing a cockpit in the middle of the vehicleand where the pilot's cockpit is therefore installed to one side of thevehicle, thereby creating a large, single payload bay in the remainingarea between the two lift-producing propellers.

According to further features in the preferred embodiments of theinvention described below an alternative vehicle arrangement isdescribed wherein the vehicle does not feature any form of pilot'senclosure, for use in an unmanned role, piloted by suitable on-boardelectronic computers or being remotely controlled from the ground.

Additional features in the exemplary embodiments relate to a centralportion of the aircraft fuselage that may be aerodynamically shaped toenhance the life characteristics of the vehicle. In one example, thecentral portion of the fuselage is airfoil-shaped to create an increasein negative pressure above the fuselage and to increase positivepressure below the fuselage, thereby providing additional aerodynamiclift.

Further features and advantages of the invention will be apparent fromthe description below. Some of those describe unique features applicablein any single or multiple ducted fan and VTOL vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 illustrates one form of VTOL vehicle constructed in accordancewith present invention with two ducted fans;

FIG. 2 illustrates an alternative construction with four ducted fans;

FIG. 3 illustrates a construction similar to FIG. 1 with freepropellers, i.e., unducted fans;

FIG. 4 illustrates a construction similar to FIG. 2 with freepropellers;

FIG. 5 illustrates a construction similar to that of FIG. 1 butincluding two propellers, instead of a single propeller, mountedside-by-side in a single, oval shaped duct at each end of the vehicle;

FIGS. 6 a, 6 b and 6 c are side, top and rear views, respectively,illustrating another VTOL vehicle constructed in accordance with thepresent invention and including pusher propellers in addition to thelift-producing propellers;

FIG. 7 is a diagram illustrating the drive system in the vehicle ofFIGS. 6 a-6 c;

FIG. 8 is a pictorial illustration of a vehicle constructed inaccordance with FIGS. 6 a-6 c and 7;

FIGS. 8 a-8 d illustrate examples of various tasks and missions capableof being accomplished by the vehicle of FIG. 8;

FIGS. 9 a and 9 b are side and top views, respectively, illustratinganother VTOL vehicle constructed in accordance with the presentinvention;

FIG. 10 is a diagram illustrating the drive system in the vehicle ofFIGS. 9 a and 9 b;

FIGS. 11 a and 11 b are side and top views, respectively, illustrating aVTOL vehicle constructed in accordance with any one of FIGS. 6 a-10 butequipped with deployable stub wings, the wings being shown in thesefigures in their retracted stowed positions;

FIGS. 11 c and 11 d are views corresponding to those of FIGS. 11 a and11 b but showing the stub wings in their deployed, extended positions;

FIG. 12 is a perspective rear view of a vehicle constructed inaccordance with any one of FIGS. 6 a-10 but equipped with a lower skirtfor converting the vehicle to a hovercraft for movement over ground orwater;

FIG. 13 is a perspective rear view of a vehicle constructed inaccordance with any one of FIGS. 6 a-10 but equipped with large wheelsfor converting the vehicle for ATV (all terrain vehicle) operation;

FIGS. 14 a-14 e are a pictorial illustration of an alternative vehiclearrangement wherein the vehicle is relatively small in size, having thepilot's cockpit installed to one side of the vehicle. Variousalternative payload possibilities are shown;

FIG. 15 is a pictorial illustration of a vehicle constructed typicallyin accordance with the configuration in FIGS. 14 a-14 e but equippedwith a lower skirt for converting the vehicle to a hovercraft formovement over ground or water;

FIGS. 16 a-16 d show top views of the vehicle of FIGS. 14 a-14 e withseveral payload arrangements;

FIG. 17 is a see-through front view of the vehicle of FIG. 16 a showingvarious additional features and internal arrangement details of thevehicle;

FIG. 18 is a longitudinal cross-section of the vehicle of FIG. 16 bshowing various additional features and internal arrangement details ofthe vehicle;

FIG. 19 is a pictorial illustration of an Unmanned application of thevehicle having similar design to the vehicle of FIGS. 16-18, but lackinga pilot's compartment;

FIG. 20 is a further pictorial illustration of an optional Unmannedvehicle, having a slightly different engine installation than that ofFIG. 19;

FIG. 21 is a top view showing the vehicle of FIG. 16 b as equipped witha extendable wing for high speed flight;

FIGS. 22 a and 22 b are side and top views, respectively, illustrating aVTOL vehicle having a plurality of lifting fans to facilitate increasedpayload capability;

FIG. 23 is a schematic view of the power transmission system used in thevehicles of FIGS. 14-19;

FIG. 24 is a schematic view of the power transmission system used in thevehicle of FIG. 20;

FIGS. 25 a-25 c show schematic cross sections and design details of anoptional single duct Unmanned vehicle;

FIG. 26 is a pictorial illustration of a ram-air-‘parawing’ basedemergency rescue system;

FIG. 27 illustrates optional means of supplying additional air to liftducts shielded by nacelles from their sides;

FIGS. 28 a-28 e are more detailed schematic top views of the medicalattendant station in the rescue cabin of the vehicle described in 14 b,14 c and 16 b;

FIG. 29 illustrates in side view some optional additions to the cockpitarea of the vehicles described in FIGS. 14-18;

FIGS. 30 a-d show a vehicle generally similar to that shown in FIG. 18,however having alternative internal arrangements for various elementsincluding cabin arrangement geometry to enable carriage of 5 passengersor combatants;

FIG. 31 shows a top view of vehicle generally similar to that shown inFIG. 30 a-d, however the fuselage is elongated to provide for 9passengers or combatants;

FIGS. 32 a and 32 b illustrate one arrangement for enabling externalairflow to penetrate a forward side of the forward duct wall;

FIGS. 32 c illustrates another configuration for airflow penetration ofthe forward duct wall;

FIGS. 32 d and 32 e illustrate a valve actuating arrangement fromopening and closing slots in the forward duct wall

FIGS. 32 f and 32 g iilustrate an alternative actuating arrangement;

FIGS 33 a and 33 b illustrate one arrangement for enabling internalairflow to exit the aft duct wall;

FIG. 33c illustrates an alternative to the configuration in FIGS. 33 aand 33 h; FIGS. 33 d and 33 e illustrate valve actuation arrangement foropening an closing slots in the aft duct wall; FIGS. 33 f and 33 g analternative actuating arrangement for opening and closing slots in t:heaft duos wall;

FIG. 34 illustrates means for directing the internal airflow to exitwith a rearward velocity component for the purpose of minimizing themomentum drag of the vehicle in forward flight;

FIGS. 35 a-c illustrate additional optional means for enabling theexternal airflow to penetrate the walls of the forward duct and theinternal airflow to exit through the walls of the aft ducted fan of thevehicles described in FIGS. 1-21 and FIGS. 30-31, while in forwardflight, for the purpose of minimizing the momentum drag of the vehicle;

FIG. 36 is a side elevation of one form of two-duct VTOL aircraftvehicle constructed in accordance with the present invention;

FIG. 37 is a top plan view of the vehicle shown in FIG. 36;

FIG. 38 is a front elevation view of the vehicle shown in FIG. 36;

FIG. 39 illustrates a longitudinal cross-section taken along line 39-39of FIG. 38;

FIG. 40 illustrates the two dimensional airflow pattern around thecross-section outer boundaries of the vehicle of FIG. 36;

FIG. 41 illustrates how suction is formed on upper surface of the centerportion of the vehicle of FIG. 36;

FIG. 42 illustrates the typical pressure coefficient distribution on anupper surface similar to the center portion of the vehicle of FIG. 36;

FIG. 43 illustrates how an external aerodynamic blister can provideadditional suction and provide extra lift to the vehicle at high speed;

FIG. 44 illustrates exemplary dimensional relationships for the blistershown in FIG. 43;

FIG. 45 illustrates the typical pressure coefficient distribution on ablister added to the upper surface of the center portion of the vehicleof FIG. 36;

FIG. 46 illustrates how, by forming the blister to have a morepronounced forward end, the direction and magnitude of the resultantsuction on the blister can be adjusted to obtain high lift with reduceddrag;

FIG. 47 illustrates exemplary dimensional relationships for the blistershown in FIG. 43;

FIG. 48 illustrates the typical pressure coefficient distribution on ablister similar to that of FIG. 48, when added to the upper surface ofthe center portion of the vehicle of FIG. 36;

FIG. 49 illustrates how, by moving the resultant lift vector of theblister forward, it is possible to also combine additional useful liftfrom the vehicle's horizontal stabilizer;

FIG. 50 illustrates an application where the internal cabin roof israised to conform with the outer limit of the blister of FIG. 46, whilealso enabling re-shaping of the cabin floor to improve flow on lowerside of vehicle;

FIG. 51 illustrates a cabin arrangement alternative to that of FIG. 50,where both occupants are facing forward, with additional clarificationsconcerning the geometry of the re-shaped cabin floor;

FIG. 52 illustrates an application where the entire center section ofthe vehicle of FIG. 36 is shaped in the form of an airfoil with asubstantially flat lower surface;

FIG. 53 illustrates exemplary dimensional relationships for the blistershown in FIG. 52;

FIG. 54 illustrates an application where the entire center section ofthe vehicle of FIG. 36 is shaped in the form of an airfoil with asubstantially concave lower surface;

FIG. 55 illustrates exemplary dimensional relationships for the blistershown in FIG. 54;

FIGS. 56 and 57 illustrate the influence of the magnitude of the inducedvelocity through the lift fans, relative to the free-stream velocity, onthe shape of the steamlines flowing around the center section, as wellas through and out of the lift fans of the vehicles of FIG. 40 and FIG.52.

It is to be understood that the foregoing drawings, and the descriptionbelow, are provided primarily for purposes of facilitating understandingthe conceptual aspects of the invention and various possible embodimentsthereof, including what is presently considered to be a preferredembodiment. In the interest of clarity and brevity, no attempt is madeto provide more details than necessary to enable one skilled in the art,using routine skill and design, to understand and practice the describedinvention. It is to be further understood that the embodiments describedare for purposes of example only, and that the invention is capable ofbeing embodied in other forms and applications than described herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As indicated earlier, the present invention provides a vehicle of anovel construction which permits it to be used for a large variety oftasks and missions with no changes, or minimum changes, required whenconverting from one mission to another.

The basic construction of such a vehicle is illustrated in FIG. 1, andis therein generally designated 10. It includes a fuselage 11 having alongitudinal axis LA and a transverse axis TA. Vehicle 10 furtherincludes two lift-producing propellers 12 a, 12 b carried at theopposite ends of the fuselage 11 along its longitudinal axis LA and onopposite sides of its transverse axis TA. Lift-producing propellers 12a, 12 b are ducted fan propulsion units extending vertically through thefuselage and rotatable about vertical axes to propel the air downwardlyand thereby to produce an upward lift.

Vehicle 10 further includes a pilot's compartment 13 formed in thefuselage 11 between the lift-producing propellers 12 a, 12 andsubstantially aligned with the longitudinal axis LA and transverse axisTA of the fuselage. The pilot's compartment 13 may be dimensioned so asto accommodate a single pilot or two (or more) pilots, as shown, forexample, in FIG. 6 a.

Vehicle 10 illustrated in FIG. 1 further includes a pair of payload bays14 a, 14 b formed in the fuselage 11 laterally on the opposite sides ofthe pilot's compartment 13 and between the lift-producing propellers 12a, 12 b. The payload bays 14 a, 14 b shown in FIG. 1 are substantiallyflush with the fuselage 11, as will be described more particularly belowwith respect to FIGS. 6 a-6 c and the pictorial illustration in FIGS. 8a-8 d. Also described below, particularly with respect to the pictorialillustrations of FIGS. 8 a-8 d, are the wide variety of tasks andmissions capable of being accomplished by the vehicle when constructedas illustrated in FIG. 1 (and in the later illustrations), andparticularly when provided with the payload bays corresponding to 14 a,14 b of FIG. 1.

Vehicle 10 illustrated in FIG. 1 further includes a front landing gear15 a and a rear landing gear 15 b mounted at the opposite ends of itsfuselage 11. In FIG. 1 the landing gears are non-retractable, but couldbe retractable as in later described embodiments. Aerodynamicstabilizing surfaces may also be provided, if desired, as shown by thevertical stabilizers 16 a, 16 b carried at the rear end of fuselage 11on the opposite sides of its longitudinal axis LA.

FIG. 2 illustrates another vehicle construction in accordance with thepresent invention. In the vehicle of FIG. 2, therein generallydesignated 20, the fuselage 21 is provided with a pair of lift-producingpropellers on each side of the transverse axis of the fuselage. Thus, asshown in FIG. 2, the vehicle includes a pair of lift-producingpropellers 22 a, 22 b at the front end of the fuselage 21, and anotherpair of lift-producing propellers 22 c, 22 d at the rear end of thefuselage. The lift-producing propellers 22 a-22 d shown in FIG. 2 arealso ducted fan propulsion units. However, instead of being formed inthe fuselage 21, they are mounted on mounting structures 21 a-21 d toproject laterally of the fuselage.

Vehicle 20 illustrated in FIG. 2 also includes the pilot's compartment23 formed in the fuselage 21 between the two pairs of lift-producingpropellers 22 a, 22 b and 22 c, 22 d, respectively. As in the case ofthe pilot's compartment 13 in FIG. 1, the pilot's compartment 23 in FIG.2 is also substantially aligned with the longitudinal axis LA andtransverse axis TA of the fuselage 21.

Vehicle 20 illustrated in FIG. 2 further includes a pair of payload bays24 a, 24 b formed in the fuselage 21 laterally of the pilot'scompartment 23 and between the two pairs of lift-producing propellers 22a-22 d. In FIG. 2, however, the payload bays are not formed integralwith the fuselage, as in FIG. 1, but rather are attached to the fuselageso as to project laterally on opposite sides of the fuselage. Thus,payload bay 24 a is substantially aligned with the lift-producingpropellers 22 a, 22 c on that side of the fuselage; and payload bay 24 bis substantially aligned with the lift-producing propellers 22 b and 22d at that side of the fuselage.

Vehicle 20 illustrated in FIG. 2 also includes a front landing gear 25 aand a rear landing gear 25 b, but only a single vertical stabilizer 26at the rear end of the fuselage aligned with its longitudinal axis. Itwill be appreciated however, that vehicle 20 illustrated in FIG. 2 couldalso include a pair of vertical stabilizers, as shown at 16 a and 16 bin FIG. 1, or could be constructed without any such aerodynamicstabilizing surface.

FIG. 3 illustrates a vehicle 30 also including a fuselage 31 of a verysimple construction having a forward mounting structure 31 a formounting the forward lift-producing propeller 32 a, and a rear mountingstructure 31 b for mounting the rear lift-producing propeller 32 b. Bothpropellers are unducted, i.e., free, propellers. Fuselage 31 is formedcentrally thereof with a pilots compartment 33 and carries the twopayload bays 34 a, 34 b on its opposite sides laterally of the pilot'scompartment.

Vehicle 30 illustrated in FIG. 3 also includes a front landing gear 35 aand a rear landing gear 35 b, but for simplification purposes, it doesnot include an aerodynamic stabilizing surface corresponding to verticalstabilizers 16 a, 16 b in FIG. 1.

FIG. 4 illustrates a vehicle, generally designated 40, of a similarconstruction as in FIG. 2 but including a fuselage 41 mounting a pair ofunducted propellers 42 a, 42 b at its front end, and a pair of unductedpropellers 42 c, 42 d at its rear end by means of mounting structures 41a-41 d, respectively. Vehicle 40 further includes a pilot's compartment43 centrally of the fuselage, a pair of payload bays 44 a, 44 blaterally of the pilot's compartment, a front landing gear 45 a, a rearlanding gear 45 b, and a vertical stabilizer 46 at the rear end of thefuselage 41 in alignment with its longitudinal axis.

FIG. 5 illustrates a vehicle, generally designated 50, including afuselage 51 mounting a pair of lift-producing propellers 52 a, 52 b atits front end, and another pair 52 c, 52 d at its rear end. Each pair oflift-producing propellers 52 a, 52 b and 52 c, 52 d is enclosed within acommon oval-shaped duct 52 e, 52 f at the respective end of thefuselage.

Vehicle 50 illustrated in FIG. 5 further includes a pilot' compartment53 formed centrally of the fuselage 51, a pair of payload bays 54 a, 54b laterally of the pilot's compartment 53, a front landing gear 55 a, arear landing gear 55 b, and vertical stabilizers 56 a, 56 b carried atthe rear end of the fuselage 51.

FIGS. 6 a, 6 b and 6 c are side, top and rear views, respectively, ofanother vehicle constructed in accordance with the present invention.The vehicle illustrated in FIGS. 6 a-6 c, therein generally designated60, also includes a fuselage 61 mounting a lift-producing propeller 62a, 62 b at its front and rear ends, respectively. The latter propellersare preferably ducted units as in FIG. 1.

Vehicle 60 further includes a pilot's compartment 63 centrally of thefuselage 61, a pair of payload bays 64 a, 64 b laterally of the fuselageand of the pilot's compartment, a front landing gear 65 a, a rearlanding gear 65 b, and a stabilizer, which, in this case, is ahorizontal stabilizer 66 extending across the rear end of the fuselage61.

Vehicle 60 illustrated in FIGS. 6 a-6 c further includes a pair ofpusher propellers 67 a, 67 b, mounted at the rear end of the fuselage 61at the opposite ends of the horizontal stabilizer 66. As shownparticularly in FIG. 6 c the rear end of the fuselage 61 is formed witha pair of pylons 61 a, 61 b, for mounting the two pusher propellers 67a, 67 b, together with the horizontal stabilizer 66.

The two pusher propellers 67 a, 67 b are preferably variable-pitchpropellers enabling the vehicle to attain higher horizontal speeds. Thehorizontal stabilizer 66 is used to trim the vehicle's pitching momentcaused by the ducted fans 62 a, 62 b, thereby enabling the vehicle toremain horizontal during high speed flight.

Each of the pusher propellers 67 a, 67 b is driven by an engine enclosedwithin the respective pylon 61 a, 61 b. The two engines are preferablyturbo-shaft engines. Each pylon is thus formed with an air inlet 68 a,68 b at the forward end of the respective pylon, and with an air outlet(not shown) at the rear end of the respective pylon.

FIG. 7 schematically illustrates the drive within the vehicle 60 fordriving the two ducted fans 62 a, 62 b as well as the pusher propellers67 a, 67 b. The drive system, generally designated 70, includes twoengines 71, 71 b, each incorporated in an engine compartment within oneof the two pylons 61 a, 61 b. Each engine 71 a, 71 b, is coupled by anover-running clutch 72 a, 72 b, to a gear box 73 a, 73 b coupled on oneside to the respective thrust propeller 67 a, 67 b, and on the oppositeside to a transmission for coupling to the two ducted fans 62 a, 62 b atthe opposite ends of the fuselage. Thus, as schematically shown in FIG.7, the latter transmission includes additional gear boxes 74 a, 74 bcoupled to rear gear box 75 b for driving the rear ducted fan 62 b, andfront gear box 75 a for driving the front ducted fan 62 b.

FIG. 8 pictorially illustrates an example of the outer appearance thatvehicle 60 may take.

In the pictorial illustration of FIG. 8, those parts of the vehiclewhich correspond to the above-described parts in FIGS. 6 a-6 c areidentified by the same reference numerals in order to facilitateunderstanding. FIG. 8, however, illustrates a number of additionalfeatures which may be provided in such a vehicle.

Thus, as shown in FIG. 8, the front end of the fuselage 61 may beprovided with a stabilized sight and FLIR (Forward Looking Infra-Red)unit, as shown at 81, and with a gun at the forward end of each payloadbay, as shown at 82. In addition, each payload bay may include a cover83 deployable to an open position providing access to the payload bay,and to a closed position covering the payload bay with respect to thefuselage 61.

In FIG. 8, cover 83 of each payload bay is pivotally mounted to thefuselage 61 along an axis 84 parallel to the longitudinal axis of thefuselage at the bottom of the respective bay. The cover 83, when in itsclosed condition, conforms to the outer surface of the fuselage 61 andis flush therewith. When the cover 83 is pivoted to its open position,it serves as a support for supporting the payload, or a part thereof, inthe respective payload bay.

The latter feature is more particularly shown in FIGS. 8 a-8 d whichillustrate various task capabilities of the vehicle as particularlyenabled by the pivotal covers 83 for the two payload bays. Thus, FIG. 8a illustrates the payload bays used for mounting or transporting guns orammunition 85 a; FIG. 8 b illustrates the use of the payload bays fortransporting personnel or troops 85 b; FIG. 8 c illustrates the use ofthe payload bays for transporting cargo 85 c; and FIG. 6 d illustratesthe use of the payload bays for evacuating wounded 85 d. Many other taskor mission capabilities will be apparent.

FIGS. 9 a and 9 b are side and top views, respectively, illustratinganother vehicle, generally designated 90, of a slightly modifiedconstruction from vehicle 60 described above. Thus, vehicle 90illustrated in FIGS. 9 a and 9 b also includes a fuselage 91, a pair ofducted-fan type lift-producing propellers 92 a, 92 b at the oppositeends of the fuselage, a pilot's compartment 93 centrally of thefuselage, and a pair of payload bays 94 a, 94 b laterally of the pilot'scompartment 93. Vehicle further includes a front landing gear 95 a, arear landing gear 95 b, a horizontal stabilizer 96, and a pair of pusherpropellers 97 a, 97 b, at the rear end of fuselage 91.

FIG. 10 schematically illustrates the drive system in vehicle 90. Thusas shown in FIG. 10, vehicle 90 also includes two engines 101 a, 101 bfor driving the two ducted fans 92 a, 92 b and the two pusher propellers97 a, 97 b, respectively, as in vehicle 60. However, whereas in vehicle60 the two engines are located in separate engine compartments in thetwo pylons 61 a, 61 b, in vehicle 90 illustrated in FIGS. 9 a and 9 bboth engines are incorporated in a common engine compartment,schematically shown at 100 in FIG. 9 a, underlying the pilot'scompartment 93. The two engines 101 a, 101 b (FIG. 10), may also beturbo-shaft engines as in FIG. 7. For this purpose, the central portionof the fuselage 91 is formed with a pair of air inlet openings 98 a, 98b forward of the pilot's compartment 93, and with a pair of air outletopenings 99 a, 99 b rearwardly of the pilot's compartment.

As shown in FIG. 10, the two engines 101 a, 101 b drive, via theover-running clutches 102 a, 102 b, a pair of hydraulic pumps 103 a, 103b which, in turn, drive the drives 104 a, 104 b of the two pusherpropellers 97 a, 97 b. The two engines 101 a, 101 b are further coupledto a drive shaft 105 which drives the drives 106 a, 106 b of the twoducted fans 92 a, 92 b, respectively.

FIGS. 11 a-11 d illustrate another vehicle, therein generally designated110, which is basically of the same construction as vehicle 60 describedabove with respect to FIGS. 6 a-6 c, 7, 8 and 8 a-8 d; to facilitateunderstanding, corresponding elements are therefore identified by thesame reference numerals. Vehicle 110 illustrated in FIGS. 11 a-11 d,however, is equipped with two stub wings, generally designated 111 a,111 b, each pivotally mounted to the fuselage 61, under one of thepayload bays 64 a, 64 b, to a retracted position shown in FIGS. 11 a and11 b, or to an extended deployed position shown in FIGS. 11 c and 11 dfor enhancing the lift produced by the ducted fans 62 a, 62 b. Each ofthe stub wings 111 a, 111 b is actuated by an actuator 112 a, 112 bdriven by a hydraulic or electrical motor (not shown). Thus, at lowspeed flight, the stub wings 111 a, 111 b, would be pivoted to theirstowed positions as shown in FIGS. 11 a and 11 b; but at high speedflight, they could be pivoted to their extended or deployed positions,as shown in FIGS. 11 c and 11 d, to enhance the lift produced by theducted fans 61 a, 61 b. Consequently, the blades in the ducted fanswould be at low pitch producing only a part of the total lift force.

The front and rear landing gear, shown at 115 a and 115 b, could also bypivoted to a stowed position to enable higher speed flight, as shown inFIGS. 11 c and 11 d. In such case, the front end of the fuselage 61would preferably be enlarged to accommodate the landing gear when in itsretracted condition. Vehicle 110 illustrated in FIGS. 11 a-11 d may alsoinclude ailerons, as shown at 116 a, 116 b (FIG. 11 d) for roll control.

FIG. 12 illustrates how the vehicle, such as vehicle 60 illustrated inFIGS. 6 a-6 d, may be converted to a hovercraft for traveling overground or water. Thus, the vehicle illustrated in FIG. 12, and thereingenerally designated 120, is basically of the same construction asdescribed above with respect to FIGS. 6 a-6 d, and thereforecorresponding parts have been identified with the same referencenumerals. In vehicle 120 illustrated in FIG. 12, however, the landinggear wheels (65 a, 65 b, FIGS. 6 a-6 d) have been removed, folded, orotherwise stowed, and instead, a skirt 121 has been applied around thelower end of the fuselage 61. The ducted fans 62 a, 62 b, may beoperated at very low power to create enough pressure to cause thevehicle to hover over the ground or water as in hovercraft vehicles. Thevariable pitch pusher propellers 67 a, 67 b would provide forward orrear movement, as well as steering control, by individually varying thepitch, as desired, of each propeller.

Vehicles constructed in accordance with the present invention may alsobe used for movement on the ground. Thus, the front and rear wheels ofthe landing gears can be driven by electric or hydraulic motors includedwithin the vehicle.

FIG. 13 illustrates how such a vehicle can also be used as an ATV (allterrain vehicle). The vehicle illustrated in FIG. 13, therein generallydesignated 130, is basically of the same construction as vehicle 60illustrated in FIGS. 6 a-6 d, and therefore corresponding parts havebeen identified by the same reference numerals to facilitateunderstanding. In vehicle 130 illustrated in. FIG. 13, however, the tworear wheels of the vehicle are replaced by two (or four) larger ones,bringing the total number of wheels per vehicle to four (or six). Thus,as shown in FIG. 13, the front wheels (e.g., 65 a, FIG. 6 c) of thefront landing gear are retained, but the rear wheels are replaced by twolarger wheels 135 a (or by an additional pair of wheels, not shown), toenable the vehicle to traverse all types of terrain.

When the vehicle is used as an ATV as shown in FIG. 13, the front wheels65 a or rear wheels would provide steering, while the pusher propellers67 a, 67 b and main lift fans 62 a, 62 b would be disconnected but couldstill be powered-up for take-off if so desired. The same applies alsowith respect to the hovercraft version illustrated in FIG. 12.

It will thus be seen that the invention thus provides a utility vehicleof a relatively simple structure which is capable of performing a widevariety of VTOL functions, as well as many other tasks and missions,with minimum changes in the vehicle to convert it from one task ormission to another.

FIGS. 14 a-14 e are pictorial illustrations of alternative vehiclearrangements where the vehicle is relatively small in size, having thepilot's cockpit installed to one side of the vehicle. Variousalternative payload possibilities are shown.

FIG. 14 a shows the vehicle in its basic form, with no specific payloadinstalled. The overall design and placement of parts of the vehicle aresimilar to those of the ‘larger’ vehicle described in FIG. 8. with theexception of the pilot's cockpit, which in the arrangement of FIG. 14takes up the space of one of the payload bays created by theconfiguration shown in FIG. 8. The cockpit arrangement of FIG. 14 afrees up the area taken up by the cockpit in the arrangement of FIG. 8for use as an alternative payload area, increasing the total volumeavailable for payload on the opposite side of the cockpit. It isappreciated that the mechanical arrangement of engines, drive shafts andgearboxes for the vehicle of FIG. 14. may be that described withreference to FIG. 7.

FIG. 14 b illustrates how the basic vehicle of FIG. 14 a may be used toevacuate a patient. The single payload bay is optionally provided with acover and side door which protect the occupants, and which may includetransparent areas to enable light to enter. The patient lies on astretcher which is oriented predominantly perpendicular to thelongitudinal axis of the vehicle, and optionally at a slight angle toenable the feet of the patient to clear the pilot's seat area and bemoved fully into the vehicle despite its small size. Space for a medicalattendant is provided, close to the outer side of the vehicle.

FIG. 14 c shows the vehicle of FIG. 14 b with the cover and side doorclosed for flight.

FIG. 14 d illustrates how the basic vehicle of FIG. 14 a may be used toperform various utility operations such as electric power-linemaintenance. In the example shown if FIG. 14 d, a seat is provided foran operator, facing outwards towards an electric power-line. Forillustration purposes, the operator is shown attaching plastic spheresto the line using tools. Uninstalled sphere halves and additionalequipment may be carried in the open space behind the operator. Similarapplications may include other utility equipment, such as for bridgeinspection and maintenance, antenna repair, window cleaning, and otherapplications. One very important mission that the utility version ofFIG. 14 d could perform is the extraction of survivors from hi-risebuildings, with the operator assisting the survivors to climb onto theplatform while the vehicle hovers within reach.

FIG. 14 e illustrates how the basic vehicle of FIG. 14 a may be used tocarry personnel in a comfortable closed cabin, such as for commuting,observation, performing police duties, or any other purpose.

FIG. 15 is a pictorial illustration of a vehicle constructed typicallyin accordance with the configuration in FIG. 14 but equipped with alower, flexible skirt for converting the vehicle to a hovercraft formovement over ground or water. While the vehicle shown in FIG. 15 issimilar to the application of FIG. 14 e, a skirt can be installed on anyof the applications shown in FIG. 14.

While FIGS. 14-15 show a vehicle having a cockpit on the left hand sideand a payload bay to the right hand side, it is appreciated thatalternative arrangements are possible, such as where the cockpit is onthe right hand side and the payload bay is on the left hand side. Allthe descriptions provided in FIGS. 14-15 apply also to such analternative configuration.

FIG. 16 illustrates four top views of the vehicle of FIGS. 14 a-14 ewith several payload arrangements:

FIG. 16 a is the basic vehicle with an empty platform on the right handside of the vehicle. FIG. 16 b shows the arrangement of the right handside compartment when configured as a rescue module. FIG. 16 c shows theconversion of the RHS compartment for carrying up to two observers orpassengers. FIG. 16 d has two functional cockpits, needed mostly forpilot's instruction purposes. It should be emphasized that similararrangements can be configured if so desired, with the pilot'scompartment on the RHS of the vehicle, and the multi-mission payload bayon the left.

FIG. 17 is a see-through front view of the vehicle of FIG. 16 a showingvarious additional features and internal arrangement details of thevehicle. The outer shell of the vehicle is shown in 1701. The forwardducted fan 1703 has a row of inlet vanes 1718 and a row of outlet vanes1717 used together to maneuver the vehicle in roll and in horizontalside-to side translation. Detail A shows, as an example, the first fivevanes being the closest to the RHS of the vehicle. These vanes are shownmounted at angles A5-A1 that are increasing progressively from nearlyvertical mounting for vane 5 to some 15 degrees of tilt shown as theangle A1 in the figure. The progressive deflected mounting of the firstrows of vanes align their chord line with the local streamlines of theincoming flow. This does not inhibit these vane's full motion to bothdirections of deflection around their basic mounting angles. It shouldalso be emphasized, that a similar, anti-symmetric arrangement of thevanes is used on the opposite side of the duct shown (LHS of thevehicle). Similarly, the vanes attached at the inlet to the aft duct,are also tilted as required to orient themselves with the local inflowangle at each transverse position along the duct, where the angle ispreferably averaged over the longitudinal span of each vane. This uniqueconfiguration of vanes can be varied in angles as a result ofaerodynamic behavior of the incoming flow and due to engineeringlimitations. This configuration can be also used with any row of inletvanes or outlet vanes installed on any single or multiple ducted fanvehicles.

The RHS engine of the vehicle 1708, is shown mounted inside itsenclosure 1702, and below the air inlet 1709. It is connected to a 90degree gearbox 1710, which is connected through a shaft (not shown) to alower 90 degree gearbox 1720. From there, through a horizontal shaft,the power is transmitted to the main gearbox 1721 that also supports thelift producing rotor 1716. A similar arrangement for the LHS engine maybe used (not shown). The pilot's compartment (cockpit) 1706 has atransparent top (canopy) of which the outer panel 1713 is hinged, topermit the pilot 1711 to enter and exit the cockpit. The pilot's seat1712 may either be normal, or a rocket deployed ejection seat tofacilitate quick egress of the pilot from the cockpit through thecanopy, if the need arises. The pilot's controls 1714 are connected tothe vehicles flight control system. The vehicle's RHS landing gear wheel1719 is shown resting on the ground, and the LHS landing gear wheel 1715is shown optionally retracted into the fuselage for reducing the drag inhigh speed flight. The vehicles two pusher fans 1704, 1705 are shownmounted on the aft portion, with the wing/stabilizer 1707 generallyspanning above and between said fans.

FIG. 18 is a longitudinal cross-section of the vehicle of FIG. 16 bshowing various additional features and internal arrangement details ofthe vehicle. The outer shell 1801 covers the whole of the vehicle, andtransitions to the engine's enclosure 1825. Inside the shell, a forwardduct 1802 and an aft duct 1803 are mounted, inside which a forward mainlift propeller 1814 and an aft main lift propeller 1813 are mounted. Theducts and propellers are preferably statically disposed within thevehicle such that they are inclined forward (generally between 5 and 10degrees although other values may be used) with respect to the verticaland rotated along the transverse axis of the vehicle, to betteraccommodate the incoming airflow at high speed. The forward duct 1802has rows of longitudinal vanes 1809 at its inlet, as well as rows oflongitudinal vanes 1810 at the exit. These vanes are predominantly usedto control the vehicle in roll as well as lateral side-to-sidetranslation. A similar set of longitudinally oriented vanes 1811 & 1812are mounted at the entrance and exit of the aft duct 1803, respectively.Optionally, additional vanes, mounted in a transverse orientation may bemounted at the exit of the forward and aft duct, shown respectively as1805 & 1804. These vanes are movable, and used to deflect the airexiting from the ducts, as shown schematically in 1815 for variousflight regimes of the vehicle. FIG. 18 is generally a cross sectionthrough the center of the vehicle looking right, although it was decidedto leave the pilot's compartment, and LHS engine and pusher faninstallation visible for reference. The lower area of the centerfuselage section of the vehicle 1808 serves as the main fuel tank. Theouter shape of this body to its fore-aft sides is molded to serve thegeometrical needs of both ducts 1802 & 1803. The lower side of thecenter fuselage has a cutout 1806 to ease the flow exiting the forwardduct 1802 to align itself with the overall air flow around the vehicleat high speed flight. The upper portion 1807 of the center fuselage 1808is suitably curved for accelerating the air entering the aft duct 1803,and thereby create a low pressure area on the top of the fuselage,relieving some of the lift production burden off the main liftingpropellers 1813 & 1814. This upper portion 1807 of the center fuselagecan also facilitates the mounting of a parachute/parafoil which will beused in emergency situations either to get to the ground safely or evento continue forward flight with the pusher fans thrust. The pilot 1818is shown seated on his seat 1831 which may either be normal, or a rocketdeployed ejection seat to facilitate quick egress of the pilot from thecockpit through the canopy, if the need arises. The pilot's controls1819 are connected to the vehicles flight control system. Also shown inFIG. 18 is one of the two the engines used in the vehicle shown as 1826mounted inside its outer shell 1825 and below the air intake 1824. The90 degree gearbox 1823 transmits the rotational power from the engine1826 to the lower gearbox through a shaft. This lower gearbox (gearbox,shaft not shown) then connects to the main aft lifting propeller gearbox1822, which also supports the propeller 1813. An interconnect shaftingmechanism (not shown) further distributes the power to the forwardgearbox 1823 that also supports the forward main lifting propeller. Alsovisible in FIG. 18 is one of the pusher fans 1827, and a cross sectionthrough the stabilizer 1828 mounted above and between the pusher fans.It can also be noticed that a curved line 1830 forms a break in thesmooth lines of the engine enclosure 1825, and the forward boundary fora deep cutout into enclosure 1825. The cutout is used to direct outsideair to the pusher fans. The general shape of the curved line 1830 canalso be seen in any one of the top views of FIG. 16. The forward end ofthe forward duct 1802 may have an optional forward facingcircumferential slot 1829 that runs generally across the forward ¼circle of the duct 1802. The slot faces the incoming flow, in a regionof the flow that is high (near stagnation) pressure. The air coming intothe slot is accelerated due to the geometric internal shape that isgenerally contracting, and is channeled through a second, inner slot1830, at an air velocity that is greater than the flow inside the duct,and generally tangentially with the inside wall of the duct 1802. Theresulting low pressure area created by this fast airflow from the slotand into the duct, affects the air above it flowing over the outer(upper) lip of the duct and provides suction to attach the latter flowto the duct's inner surface, and avoid flow separation at high speed. Asecond role played by the slots 1829 & 1830 is to direct some of the airflowing through duct 1802 through an additional opening, therebyreducing the amount of air flowing in above the duct's lip, and so alsoreducing the overall pitching moment (having an adverse effect on thevehicle) created by the forward duct at high speed flight. It should benoted that the slot 1829 may also have an optional door or doors tofacilitate opening of the bypass airflow only as flight speed isincreased. Such door/doors, if used, my be activated externally throughan actuator or mechanism, or alternatively rely on the pressuredistribution and difference between the inside and outside of the duct,to self-activate a spring loaded door or doors, as required. The landinggear wheels 1821 & 1820 are shown in the landing gear's extendedposition. An option (not shown) exists for retracting all four landinggears into the fuselage shell 1801 to reduce drag in high speed flight.

FIG. 19 is a pictorial illustration of an Unmanned application of thevehicle. Evident in the picture is the vehicles outer shell 1901 that islacking any pilot's enclosure. Also visible is the forward duct 1909with the rows of longitudinally mounted inlet vanes. The RHS engineenclosure 1903 is shown with an intake 1904 generally installed close tothe top and to the front of the engine enclosure 1903. A similararrangement can be seen for the LHS engine enclosure 1902 and the LHSengine intake port 1905. Two pusher fans 1906 & 1907 are shown, with astabilizer 1908 spanning between them. The vehicle's fixed skid typelanding gear is shown in 1910, and a typical pictorial installation ofan observation system in 1911.

FIG. 20 is a further pictorial illustration of an optional Unmannedvehicle, having a slightly different engine installation than that ofFIG. 19. Here, in a manner similar to that of FIG. 19, the fuselageouter shell 2001 is also lacking a pilot's compartment. However, thevehicle's engine is mounted inside the fuselage in the areaschematically shown as 2006. An air intake 2005 supplies air to theengine. Two pusher fans 2006 & 2007 are used, as well as a stabilizer2008. The forward duct 2002 and aft duct 2003 have longitudinallymounted vanes. A typical pictorial installation of an observation systemis shown in 2009. The vehicle's fixed skid type landing gear is shown in2010.

FIG. 21 is a top view showing the vehicle of FIG. 16 b equipped with anextendable wing for high speed flight. The RHS wing is designated 2101in the extended position and 2102 when folded under the fuselage. Anactuator 2103 is used for extending and retracting the wing as desired.The LHS wing is similar, as evident in the drawing.

FIG. 22 a-22 b are side and top views, respectively, illustrating a VTOLvehicle that employs a plurality of lift generating fans, arranged onebehind the other, all connected to a common chassis, for the purpose ofcarrying an increased payload over that which is possible with twolifting ducted fans. A chassis designated 2001 houses a number of ductedfans 2002 for generating lift. The fans may be tilted slightly forwardas shown in FIG. 22 a to achieve higher speed in cruise. Two elongatedcabins 2003 and 2004 are preferably located on both sides of the ductedfans to accommodate passengers or other cargo. A pilot 2005 may beseated in a cockpit 2006 at the front end of one of the cabins, such asthe left cabin 2004. Two engines 2012 are located to the aft of thecabins and have air intakes 2013. Two variable pitch pusher fans 2014,enclosed in shrouds, are mounted to the rear of the cabins. A stabilizer2015 is mounted between the pusher fans to facilitate nose-down trimmingmoments in forward flight. Multiple inlet roll, yaw and side forcecontrol vanes 2007 are preferably mounted longitudinally in all ducts,supplemented by similar vanes 2008 at the duct's exits. Transversallymounted guide vanes 2009 may also be mounted to reduce friction lossesand flow separations of the flow exiting from the ducts. Side openings2016 may be optionally installed to enable outside air to be mixed withinflow from above, reducing the impact that the cabins may have onthrust augmentation of the ducted fans as well as the controleffectiveness of the vanes installed in the inlets to these ducted fans.A variable pitch fan (rotor) 2010 is mounted in each duct. Preferably,one half of the fans (or as close to half as possible, such as in thecase of a vehicle similar to that shown in FIG. 22 but having an oddnumber of lifting ducted fans) turn in the opposite direction as theother half. A plurality of landing gears 2001 support the vehicle on theground and serve to attenuate the landing impact. Some of the wheelsemployed in the landing gear may be powered, or alternatively, forwardground movement can be accomplished through the use of the variablepitch pusher fans.

FIG. 23 shows an optional arrangement of a power distribution system fortransmitting the power from each of the rear mounted engines to the twolifting fans and two pusher fans such as found in the vehicles shown inFIGS. 14-19. As can be seen, two engines 2303 are preferably used todrive the two main lift rotors and the two pusher fans through a seriesof shafts and gearboxes. The power takeoff (PTO) of each engine isconnected through a short shaft 2315 to the RHS and LHS AftTransmissions designated 2302 and 2301 respectively. From thesetransmissions, the power is distributed both to the aft pusher propsthrough diagonally oriented shafts 2304 as well as to the Aft RotorGearbox 2307 through two horizontally mounted shafts 2306. The two mainlift rotors are connected to their respective gearboxes through propflanges 2308. The shaft interconnecting both main lift rotors is dividedinto two segments designated as 2309 and 2312, connected by a CenterGearbox 2310 through flexible joints. This center gearbox serves mainlyto move the rotation center in parallel and connect both shafts 2309 and2312 without affecting the direction of rotation (i.e. employing anuneven number of plane gears mounted along its length). At least one ofthe intermediate gears in Center Gearbox 2310 has a shaft that is opento the outside designated as 2311, enabling power for accessories oneither side of the face of Gearbox 2310, resulting in opposingdirections of rotation (rotorsnot shown). The rotors preferably turn inopposite directions to eliminate torque imbalance on the vehicle.

FIG. 24 shows an optional arrangement of a power distribution system fortransmitting the power from a centrally mounted engine, or from twoengines forming a ‘twin-pack’, to the two lifting fans and two pusherfans such as found in the vehicles typical of FIG. 9 and FIG. 20. As canbe seen, the engine, designated as 2401 is used to drive the two mainlift rotors and the two pusher fans through a series of shafts andgearboxes. The power takeoff (PTO) of the engine designated as 2408 isconnected through a short shaft to a central Transmission designated2402. An extension of the same shaft designated as 2409 transmits powerdirectly to the forward lift fan gearbox designated as 2410. From thecentral transmission 2402, the power is distributed both to the aft liftfan gearbox through a shaft designated as 2406 as well as to two angledgearboxed such as 2404 through two horizontally mounted shafts 2403.From the angled gearboxes, two diagonal shafts 2405 transmit power tothe aft pusher prop gearboxes 2405. The central transmission 2402 mayalso have an additional shaft that is open to the enabling power foraccessories (rotors not shown). The rotors preferably turn in oppositedirections to eliminate torque imbalance on the vehicle.

FIG. 25 a shows a schematic cross section and design details of anoptional single duct unmanned vehicle. The vehicle includes a powerplantdesignated as 2502, which may be based on turboshaft technology as shownschematically in FIG. 25 a, although other means of propulsion arepossible. A circumferential duct designated as 2501 surrounds the rotor(lifting fan) designated as 2504. The duct 2501 may also serve to housethe flight control and communication equipment as well as the fuel forthe duration of the mission. A fuel sump with pump is designated as2505. A gearbox designated as 2503 is used to reduce the rotationalspeed of the engine's shaft to match that required by the fan 2504. Twolayers of vanes (2506 and 2508) are used to control the vehicle in roll,pitch, yaw and lateral and longitudinal translations. The vanes layersare preferably oriented in multiple planes as will be explained withreference to FIG. 25 c. A payload typically consisting of a video cameramay be housed in the clear spherical compartment designated by 2512.

FIG. 25 b shows an alternative lifting fan arrangement where two rotors2510 and 2511 rotate in opposite direction to cancel the torque effectthat one fan, such as 2504, would have on the vehicle. A slightly largergearbox designated as 2509 is used to rotate the two rotors in oppositedirections through concentric shafts.

FIG. 25 c shows different arrangements of vanes in the inlet to theduct, generally designated as view “A” in FIG. 25 a, but also typicalfor the bottom (exit) layer of vanes 2508. While the arrangements ofFIG. 25 c show a number of possibilities, many additional arrangementsare possible. The common principle in the in-plane vanes arrangements ofFIG. 25 b designated 2513 thru 2519 is that typically one half of thevanes are oriented at an angle (typically 90 degrees but other anglesare possible) to the other half, so as to produce any combination offorce components that will result in a single equivalent force in anydirection and magnitude in the plane of the vanes, be it the inlet vanesdesignated as 2506 in FIG. 25 a or the exit vanes designated as 2508 inFIG. 25 a. Various vane configurations are possible, such as the squarepattern in FIG. 2516, the cross pattern in FIG. 2517, and the weavepattern in FIG. 2518.

FIG. 26 is a pictorial illustration of a ram-air-‘parawing’ basedemergency rescue system. In an emergency, or for other purposes such asextended range, the ducted fan vehicle (manned or unmanned) designatedas 2601 need not rely on its lifting fans (2606) to generate lift, butmay instead release a lift generating ram-air ‘parawing’ shownpictorially and designated as 2605. Optionally, the ‘parawing’ may besteered through the use of steering cables shown schematically anddesignated as 2607. In the event that the vehicle's pusher fansdesignated as 2602 are operative, the vehicle can carry on in levelflight to its destination. Upon reaching its destination, the vehiclecan release the ‘parawing’ (2605) and continue flying using its liftfans (2606), or may elect to land using the ‘parawing (2605) stillattached to the vehicle. Alternatively, if the pusher fans (2602) arenot producing sufficient thrust, the ‘parawing’ (2605) will glide thevehicle down to land, preferably extending its glide ratio significantlyover a spherical ‘standard’ parachute.

FIG. 27 illustrates optional means of supplying additional air to liftducts shielded by nacelles or aerodynamic surfaces from their sides,typical of the aft lift fans of the vehicles described in FIGS. 1, 5, 6,8, 9 and 11-22. In FIG. 27, a lift generating ducted fan designated as2703 is preferably partially shielded from the air around it by anacelle 2702. Openings for the air, designated as 2704 and 2705, permitoutside air to flow (2707) in through a channel (2706) from the sidesand combine with the inflow from above (2708) to create relativelyundisturbed flow conditions for the ducted fan (2703). With the openings2704 and 2705 in place, the impact of the nacelle on thrust augmentationof the ducted fan as well as the control effectiveness of the vanes isminimized. Preferably, the exit portions of openings 2704 and 2705 meetand is substantially aligned with an upper lip of the duct of ducted fan2703.

FIGS. 28 a-28 e are more detailed schematic top views of the medicalattendant station in the rescue cabin of the vehicle described in 14 b,14 c and 16 b. FIG. 28 a shows schematically how the cabin is laid outwith respect to the vehicle. FIG. 28.b illustrates the medical attendantdesignated as 2802 seated facing forward, resting his/her arms on table2801, FIG. 28 c shows the medical attendant in seat's intermediateposition, enabling medical attendant to reach comfortable the chest andabdomen area of patient designated as 2803, lying on a litter/stretcherthat is free to move along a rail on table 2801, and can be locked inplace in any intermediate position. FIG. 28 d shows the medicalattendant in extreme rotated position (2805), and patient litter movedto extreme ‘inside cabin’ position, to enable medical attendant to reachpatient head from behind, necessary for performing procedure of clearingpatient's airways. FIG. 28 e is a schematic depiction of a swivelingseat 2806 that can be used by medical attendant 2802. Also shownschematically in FIG. 28 e is patient's litter 2807 that is able to movealong guiding rail 2810 guided by four wheels or rollers 2814, althougha different number of wheels or rollers can be used. When the attendantis facing forward, as 2802 in FIG. 28 b, and for example when there isno patient on board, the seat 2806 in FIG. 28 e swivels to its rightmostposition as schematically shown in 2811. When the litter is loaded it isnormally placed as shown pictorially in FIG. 28 a, and schematically as2808 in FIG. 28 e. In this position, the attendant 2802 swivels on seat2806 to intermediate position 2813 and has access to patient's chest andabdomen. This seat position corresponds to attendant's position shownpictorially in FIG. 28 c as 2804. When need arises for attendant toreach the head of patient 2803 from behind, the litter 2807 is movedalong track 2810, while attendant now shown in FIG. 28 c as 2805 swivelsseat 2806 to leftmost position, shown schematically in FIG. 28 e as2812.

FIG. 29 illustrates in side view various optional additions to thecockpit area of the vehicles described in FIGS. 14-18. The pilotdesignated as 2901 is shown together with optional room for a crewmember or passenger 2902 behind the pilot. Also shown are the medicalattendant 2903, and the patient lying in an extreme ‘inside cabin’position 2904 on the cabin table 2905. The cockpit floor designated as2906 may be sealed to separate the pilot's compartment from the cabin.

FIGS. 30 a-d show a vehicle that is generally similar to that shown inFIG. 18, but which shows alternative internal arrangements for variouselements including cabin arrangement geometry to enable carriage ofpassengers or combatants. FIG. 30 a is a top view schematically showingthe position of each occupant. FIG. 30 b is a longitudinal cross sectionshowing placement of equipment and passengers inside the vehicle, andFIGS. 30 c and 30 d are local lateral sections of the vehicle. A typicalpassenger or combatant 3002 is shown in FIG. 30 c. The top of the cabin3001 is raised above that of FIG. 18 to accommodate passengers orcombatants in center section of vehicle. A single main transmission unit(3004) is shown that is an alternative power transmission scheme to thatof FIG. 18. Power is transmitted from engine 3003 to main transmissionunit 3004. One angled shaft 3005 transmits power to the aft pusher fan3009, and a second, generally horizontal shaft 3006 transmits power tothe aft lift rotor gearbox 3010. The shaft 3006 is housed inside airfoilshaped housing 3008 that also supports mechanically the aft lift rotorgearbox 3010. A center fuselage secondary transmission 3007 is connectedto each of the main lift rotor gearboxes 3010, 3011, and also housesattachment for auxiliary equipment.

FIG. 31 shows a top view of vehicle generally similar to that shown inFIG. 30 a-d, but where the fuselage is elongated to provide for 9passengers or combatants.

FIGS. 32 a-g illustrate means for enabling the external airflow topenetrate the forward facing side 3201 of the forward ducted fan of thevehicles described in FIGS. 1-21 and FIGS. 30-31 while in forwardflight. One configuration that may be used to obtain such airflowpenetration is shown in FIG. 32 b and generally also shown at theforward end of FIG. 32 a. Rows of generally vertical open slots 3204 forenabling throughflow of air are shown, with remaining duct structureincluding an upper lip 3202 and a lower ring 3205. Airfoil shapedvertical supports 3203 serve to stabilize the structure and provideprotection for the fan inside the duct. The slots 3204 remain open atall times. A second configuration for obtaining such airflow penetrationis shown in FIG. 32 c where the whole forward wall of the forward ductis cut to obtain two generally rectangular openings 3206 with anoptional center support 3207. An additional option, which is anexpansion of the method of FIG. 32 b, is shown in FIGS. 32 d and 32 ewhere externally actuated rotating valves 3208 are mounted inside eachslot 3204. When the vehicle is hovering, the slots are closed by thevalves as shown in FIG. 32 e. When the vehicle is in forward flight andflow of air into the duct is desired, the externally actuated valves3208 rotate to the ‘open’ position shown in FIG. 32 d, where the airflow3209 is free to flow through the slots. An alternative to the concept ofFIGS. 32 d-e, is shown in FIGS. 32 f-g where each of the verticalsupports 3203 is attached to upper lip 3202 and lower ring 2305 byhinges that enable multiple vertical supports to pivot around multiplevertical axes 3210 and assume the position shown in FIG. 32 g, where themultiple slots 3204 are closed to the external airflow.

FIGS. 33 a-e illustrate alternative means for enabling the internalairflow to exit through the walls of the aft ducted fan of the vehiclesdescribed in FIGS. 1-21 and FIGS. 30-31, while in forward flight. Oneconfiguration for obtaining such airflow exit is shown in FIG. 33 b andgenerally also shown at the aft end of the vehicle shown in FIG. 33 a.Rows of generally vertical open slots 3304 for enabling exit of air areshown, with remaining duct structure including upper lip 3302 and lowerring 3305. Airfoil shaped vertical supports 3303 serve to stabilize thestructure and provide protection for the fan inside the duct. The slots3304 preferably remain open at all times. A second possible option ofobtaining such airflow exit is shown in FIG. 33 c where the whole rearwall of the aft duct is cut to obtain two generally rectangular openings3306 with an optional center support 3307. An additional option, whichis an expansion of the method of FIG. 33 b, is shown in FIG. 33 d andFIG. 33 e where externally actuated rotating valves 3308 are mountedinside each slot 3304. When the vehicle is hovering, the slots areclosed by the valves, as shown in FIG. 33 e. When the vehicle is inforward flight and exit of air through the duct wall is desired, theexternally actuated valves 3308 rotate to the ‘open’ position, as shownin FIG. 33 d, where the airflow 3309 is free to flow through the slots.An alternative to the concept of FIGS. 33 d-e is shown in FIGS. 33 f-gwhere each of the vertical supports 3203 is attached to upper lip 3202and lower ring 2305 by hinges that enable multiple vertical supports topivot around multiple vertical axes 3210 and assume the position shownin FIG. 33 g, where the multiple slots 3204 are closed to the externalairflow. As made apparent in FIGS. 32 b, 32 c, 33 b and 33 c, theopenings in the duct wall extend both upstream and downstream of the fanor propeller.

FIGS. 34 a-c illustrate alternative means for directing the internalairflow to exit with a rearward velocity component for the purpose ofminimizing the momentum drag of the vehicle in forward flight. As shown,the lower forward portion of the forward duct 3401 is curved back at anangle that increases progressively along the circle-shaped forward ductwall, reaching a maximum angle at the center section. The curvature mayvary from vertical all around the duct, such as at hover, to 30-45degrees from vertical inclined backwards at center and decreasingprogressively to the sides of the duct. In a similar manner, the lowerforward center fuselage 3402, the lower aft portion of the centerfuselage 3403 and the lower aft portion of the aft duct 3404 are curvedback to direct the flow exiting from the ducts to better align with theincoming flow when the vehicle is in forward flight. The abovegeometrical reshaping of the ducts exits may be fixed (i.e. built intothe shape of the ducts) as in FIG. 34 a, or alternatively, may be ofvariable geometry such as flexible lower portion of ducts as shown inFIG. 34 b. Various means of obtaining change of geometry to said lowerduct portion are available. One option, illustrated in FIG. 34 b showsthe upper, fixed part of the duct 3405, to which is attached a flexibleor segmented lower part 3406. The outer sleeve 3408 of a flexible‘push-pull’ cable 3407 is connected to bottom of the flexible orsegmented lower part 3406, whereby an actuator 3409, or optionally twoactuators shown schematically as 3409 and 3410, mounted inside thefuselage would pull the cable 3407, thereby affecting the geometry ofthe duct as desired. The lower aft portion of the center fuselage 3404is moved back in a manner similar to the lower forward portion of theforward duct 3401 as explained, but with the difference that moving theaft duct lower part backwards involves pushing a flexible ‘push-pull’cable rather then pulling by the actuator/s from inside the fuselage, aswas the case in FIG. 34 b.

FIGS. 35 a-c illustrate additional alternative means for enabling theexternal airflow to penetrate the walls of the forward duct and theinternal airflow to exit through the walls of the aft ducted fan of thevehicles described in FIGS. 1-21 and FIGS. 30-31, while in forwardflight, for the purpose of minimizing the momentum drag of the vehicle.As shown in FIG. 35 a, the forward part of the forward duct has an uppersection 3501, an opening for incoming airflow 3502 and a lower ring3506. Similarly, the aft portion of the aft duct has an upper section3504, an opening for incoming airflow 3505 and a lower ring 3506.Optional center supports 3509, 3510 are provided at the forward and aftducts respectively for supporting the lower rings 3503 and 3506. FIGS.35 b and 35 c show an enlarged cross-section through the forward ductwith an optional flow blocker 3507. Flow blocker 3507 is preferably arigid, curved barrier that slides up into the upper lip when in forwardflight, and slides back down to block the flow when in hover.

FIG. 35 c shows how the flow blacker 3507 is mechanically lowered, suchas by actuators or other means not shown, to engage ring 3506 or othersimilar means on lower ring to block the external airflow, and preservethe straight cylindrical shape of the ducts down to the duct exits,while the vehicle is in slow flight or hover. A similar arrangement canbe applied to the aft end of the aft duct. It is appreciated that flowblocker 3507 can either be one piece for each duct, or divided into twosegments, such as where the option of adding vertical supports 3509 and3510 is used.

The vehicle illustrated in FIGS. 36-41 is a VTOL aircraft carrying aducted fan lift producing unit 3601 at the front and a second similarlift producing unit 3602 at the rear. In addition, the vehicle featurestwo ducted-fan thrusters 3603 and 3604 located at the rear, and ahorizontal stabilizer 3605 for providing pitch stability to the vehicle,that also features movable flaps 3606 for creating additional liftthrough flap deflection. The stabilizer 3605 may also be optionallypivoted as a unit around pivots shown at 3707. Alternatively or inaddition to the movable flaps and pivotal stabilizer, there may be otheraerodynamic means of flow control such as air suction or blowing,piezoelectric, or other actuators or fluidic controls. The vehicle ofFIGS. 36-41 also features a compartment, such as a passenger cabin 3608,occupying the central portion of the vehicle, being below andsubstantially to the side of the pilot's compartment 3609. Alongitudinal cross section, designated as A-A is marked on FIG. 36 andis shown in FIG. 42 but with the landing gear omitted).

FIG. 39 shows the longitudinal cross section A-A from FIG. 36,illustrating the forward lift fan duct 3610, the rear lift fan duct 3611and the central cabin 3608 showing by way of example only a forwardfacing passenger at 3612, a rear facing passenger 3613 and the cabinheight h at 3614, providing sufficient room and head clearance for thevehicle's occupants. The outer upper and lower boundaries of the cabin3608 shown at 3615 and 3616 respectively are functionally configured toprovide a substantially constant cabin height thereby featuring arelatively flat surface substantially aligned with the longitudinal axisof the vehicle, and preferably substantially parallel to the air flowlines during the flight in order to reduce drag, on both the roof 3615and the floor 3616 of said occupant's cabin.

FIG. 40 illustrates the air flow around the cabin 3608 at forwardcruise. While airflow that is distant from the vehicle shownschematically by the streamlines at 3617 is undisturbed by the vehicle,closer streamlines are affected by the vehicles shape and the action ofthe forward and rear lift fans. Those include the air entering theforward duct 3610 shown schematically at 3618, air flowing over thecabin 3608 and then entering the rear duct 3611 shown schematically at3619. A stagnation point shown schematically at 3620 is always present,where all air below the streamline ending at this stagnation point flowsover the cabin roof, with some of it continuing aft and some of itflowing into the rear lift duct 3611. It should be noted that due to theabrupt change in the vehicle's contour at the exit of the flow from theforward duct, the flow cannot make the turn and remain attached to thebottom of the cabin. Instead, in the region shown at 3621, the flowcontinues its downward motion, and only at a distance from the vehicle,turns gradually back to align itself with the incoming free-stream flow.This separation of flow from the bottom of the cabin 3608 causesconsiderable drag and especially momentum drag increase to the completevehicle in forward cruise flight. It should further be explained thatthe flow patterns described in FIG. 40 are not limited to the centersection A-A, but are generally prevailing across the width of thevehicle's cabin, creating essentially 2-dimensional flow with nospill-over to the sides of the vehicle. This is caused predominantly bythe suction effect of the lift fans, with the rear fan being the majorcontributor. A secondary contributing factor to the absence ofspill-over from the center section is the raised side canopies orcockpits 3609, 3622 shown in FIGS. 36-39. However, it will be emphasizedthat the 2-dimensional flow with no spill-over to the sides prevailsalso in vehicles which do not have raised or elevated side canopies orroof shape which resembles the vehicles shown in FIGS. 36-39, and thepresent invention applies also to such vehicles. Furthermore, the flowin FIG. 40 is shown fully attached to the surface even behind the cabin,with no separation which again would not be possible at high speedcruise without the rear fan acting to create the suction that attachesthe flow to the vehicle's surface.

FIG. 41 illustrates the influence that streamlines flowing over thecabin roof have on the local air pressure adjacent to the vehicle'souter surface. Shown at 4101 and 4102 are two typical low pressureareas, created by the acceleration of the airflow over the forwardcurved end of the cabin 3608, and once more when the air accelerates asit goes around the curved rear end of the cabin. Because the roof of thecabin is substantially flat, the area directly above the cabin does notexperience substantial changes in air pressure. As a result of the lowpressure areas 4101 and 4102, two resultant suction forces develop,shown schematically at 4103 and 4104, that act by the air on thevehicles outer surface, with the net effect of some additionalaerodynamic lift.

FIG. 42 illustrates the results of Navier-Stokes analysis of thepressure coefficient distribution on a flat upper surface shown at 4201similar to the top of the center portion of the vehicle of FIG. 36. Ascan be seen, a low negative pressure peak shown in absolute values at4202 is formed on the front end of the upper surface, reducing tomoderate pressure on the flat surface, and increasing back to highsuction Cp as the flow makes the rear curve of the roof, down towardsthe lift fan. A slight disturbance in the smoothness of the Cp curve isnoticeable at 4203, caused by local flow separation, which is howeverquick to re-attach to the surface of the vehicle before entering therear lift fan.

FIG. 43 illustrates a modification to the outer roof line where a convexsurface configuration, or “blister” 4301 is added on top of thesubstantially flat roof contour 4303. (Roof contour 4302 has theidentical or substantially identical shape of roof 3615 of FIG. 39) Dueto the presence of the blister and continuous convexness obtained on theouter surface, a new low pressure region is now created shownschematically as 4303, with an additional suction force 4304 providingadditional lift to the vehicle. It should be noted that the low pressurearea 4303 and all resultant forces are shown schematically merely toillustrate the mechanism by which additional lift is obtained throughthe addition of blister 4301 on the cabin roof. Shown at 4401 in FIG. 44are some characteristics relating to the geometry of the blister 4301.Shown is substantially constant upper circular arc with radius R, withmaximum thickness occurring substantially at midpoint so that C˜=½A, andvalue of R to obtain a ratio between maximum thickness B andlongitudinal measure A substantially in the range of B/A˜=0.20-0.40.

FIG. 45 illustrates the results of Navier-Stokes analysis of thepressure coefficient distribution on a curved upper surface shown at4501 similar to the top of the blister 4301 of FIG. 43. The originalflat cabin roof is shown for reference at 4502. As can be seen, a lownegative pressure shown in absolute values at 4503 begins to form on thefront end of the upper surface, but unlike the pressure distribution ofFIG. 42, the pressure keeps increasing to high suction Cp, reaching amaximum value approximately over the highest portion of the blister. Asin FIG. 42, also here a slight disturbance in the smoothness of the Cpcurve is noticeable at 4504, however more prominent than that of FIG.42, also caused by local flow separation, which is however quick tore-attach also here to the surface of the vehicle before entering therear lift fan.

FIG. 46 shows a modification on the shape of the blister, shown here at4601, not being substantially symmetrical as blister 4301 of FIG. 43,but having an intentional forward inclination, where the radius ofcurvature of the blister outer surface that is closer to the incomingair is smaller, and thereby the front facing curvature of the blister4601 is steeper and less gradual than the curvature of its rear portion.As a result, the acceleration of air over the forward part of blister4601 is faster, and the low pressure area created shown at 4602 haslower pressures than on the standard flat roof while acting on asimilarly sized portion of the vehicle's body, thereby creating astronger lift force shown schematically at 4603, while, unlike for thesymmetrical blister of FIG. 43, also having this resultant angledforward to create a positive propulsive force component in the directionof flight, in addition to the lift force component. It should again beemphasized that the shapes of the low pressure regions and size anddirection of resulting forces are shown schematically merely toillustrate the mechanism by which additional lift is obtained throughthe low pressure field created by the presence of the blister on top ofthe substantially flat standard cabin roof.

Shown at 4701 in FIG. 47 are some characteristics relating to thegeometry of the blister 4601. Shown is non-constant upper circular arcwith smaller radius of curvature R at the forward area of the section,with typical values so as to obtain maximum thickness occurringsubstantially in the range of distances from the forward edge C˜=0.2A-0.3 A, while at the same time obtaining a desired ratio betweenmaximum thickness B and longitudinal measure A, substantially in therange of B/A˜=0.20-0.40.

FIG. 48 illustrates the results of Navier-Stokes analysis of thepressure coefficient distribution on a curved upper surface shown at4801 similar to the top of the blister 4601 of FIG. 46. The originalflat cabin roof is shown for reference at 4802. As can be seen, a lownegative pressure shown in absolute values at 4803 begins to form on thefront end of the upper surface, rises steeply, and reaches a maximumvalue approximately over the highest portion of the blister. As in FIGS.42 and 45, also here a slight disturbance in the smoothness of the Cpcurve is noticeable at 4808, also caused by slight local flowseparation, which is however quick to re-attach also here to the surfaceof the vehicle before entering the rear lift fan.

FIG. 49 illustrates how a forward inclined blister similar to the oneshown at 4601 in FIG. 46 also has the effect of moving forward the netlift force shown as L1 acting on the roof through the blister, relativeto the substantially symmetric blister shape shown at 4301 on FIG. 43.Because the Center of Gravity of the vehicle, shown at 4902 around whichthe vehicle rotates as a free body, is located substantially at thecenter of the vehicle, an eccentricity shown as e1 develops between thelien of action of force L1, shown at 4903 and the Center of Gravity4902. As a result, a positive, nose-lifting pitching moment develops asa result of the forward lift line location of the blister, which needsto be counteracted to maintain the balance of the vehicle in pitch. Thisis where additional lift shown as L2 can easily be generated by thehorizontal stabilizer shown at 4904, that, together with eccentricity e2of L2 relative to the Center of Gravity 4902, can counter-balance thepitching moment caused by L1. The beneficial result of this is that anadditional lift force L2 is now acting on the vehicle, furtherincreasing the lift at cruise, keeping in mind that the horizontalstabilizer 4904 could not have been used to create lift, had there beenno counter such as the forward inclined blister 4601 maintaining therequired balance of moment around the vehicle's Center of Gravity.

FIG. 50 illustrates how, if the forward inclined blister shown at 4601in FIG. 46 is made hollow to effectively create a modified cabin roofsubstantially in the shape of the blister shown at 5001, the rear facingoccupant shown at 5002 can now be raised relative to the forward facingoccupant 5003, yielding an added benefit of being able to reconfigurethe floor of the cabin in a manner shown at 5004 and further explain inFIG. 51, thus providing smooth outflow of the air, shown schematicallyat 5005 from the exit of the forward duct, resulting in reduction of thedrag and especially momentum drag of the vehicle in cruise.

FIG. 51 illustrates that the invention is not limited to rear facingoccupants, and that both occupants shown at 5101 and 5102 can also beforward facing, or in fact be seated in any intermediate position in thecabin. It should be emphasized that the occupants herein described, byway of example only, can be replaced by cargo or by any other cabin orpayload bay function or contents. Also further explained in FIG. 51 isthe geometry of the reconfigured floor common to FIGS. 50 and 51. It canbe seen that as soon as the forward duct inner surface clears the tip ofthe propeller blades shown schematically at 5103, the outer boundary ofthe cabin begins to curve backwards at point marked by 5104, andcontinues aft at a shallow angle, merging with the original flat cabinbottom at a point marked by 5105, which is substantially aft of theforward end of the cabin. It can be noticed that the radius of curvatureat the start close to point 5104 is small (i.e., relatively sharpcorner), followed by a relatively flat (large radius of curvature) slopedown to point 5105. This relatively flat angled bottom, rather than aconstant arc chosen for the cabin floor achieves two purposes: a. Therelatively sharp curve in the contour close to point 5104 facilitatesearly separation of the flow from the forward bottom surface of thecabin when the vehicle is in hover, thereby not creating any flowdistortion or unwanted interaction with the fuselage below the propeller2. b. When in forward flight, with the flow attached, the relativelyflat diagonal surface between points 5104 and 5105 avoids the build upof low pressure and suction on that surface which would have resulted innegative lift, had that contour been of substantially constant radius.

It should also be noted that the ratio L1/L2 is substantially in therange of 0.30-0.60, and that the reconfigured diagonal cabin floor linebetween points 5104 and 5105 is substantially longer than would be thecase if only a local bend to avoid a sharp corner were introduced to theforward end of an otherwise flat cabin floor (i.e., L1/L2=1).

FIG. 52 illustrates an alternative cabin shape, where the upper cabinroof at 5201 is still curved substantially in the form of FIG. 46, butwhere the bottom of the cabin area shown at 5202 is substantially flat.While not directly suitable to accommodate the occupants shown in FIGS.50, 51, the flat bottom cabin shape could still be used for otherapplications such as cargo or unmanned applications of the vehicle, oralternatively—for larger size vehicles, where the cabin shape wouldstill be high enough to provide headroom for human occupants. Thegeometry of the flat bottomed cabin is shown schematically at 5301 inFIG. 53, with the ratio of t/c substantially in the ranget/c−=0.30-0.50. The main aerodynamic advantage of the flat bottom 5202over the curved bottom shown at 5004 on FIG. 50 is the avoidance ofdownward suction forces, with better ratios of lift to drag obtained inforward cruise.

FIG. 54 illustrates a further variation on the cabin floor shape, wherethe bottom is concave, shown at 5401. While the concavity of the floorhas the disadvantage of further reducing the available cabin innerheight and useful space, it has the aerodynamic advantage of increasingthe positive pressure on the bottom of the cabin, and potentiallyfurther improving the lift to drag ratio over the flat bottom of FIG.52. The geometry of the concave bottomed cabin is shown schematically at5502 in FIG. 55, with the ratio of t/c as before, i.e., substantially inthe range t/c˜=0.30-0.50, and with the section's concavity ratio s/csubstantially in the range s/c˜=0.05-0.15.

FIG. 56 and FIG. 57 illustrate the influence of the magnitude of theinduced velocity, relative to the free-stream velocity, on the shape ofthe streamlines flowing around the center section, as well as throughand out of the lift fans of the vehicle, FIG. 56 representing thevehicle with cabin shape of FIG. 40 and FIG. 57 representing the vehiclewith cabin shape of FIG. 52. Shown in FIG. 56 at 5601 is high inducedvelocity flowing through the blades shown schematically at 5602 of therear fan shown schematically at 5603. A similar description isapplicable to the forward fan of the vehicle. In FIG. 57, a smallerinduced velocity shown at 5701 flows through the fan, as would forexample result if additional lift on the cabin roof shown schematicallyat 5702 would occur at high speed, without a corresponding increase inthe vehicle's weight, which would require the total lift to remain thesame, necessitating in reduction of the lift contribution of thefans—hence a reduction in induced velocity through the fan blades.Because the change in induced velocity between FIGS. 56 and 57 isessentially at constant flight speed, one can see from the airspeedvector diagrams shown that while free stream velocity shown at 5604 and5703 remains unchanged in magnitude, the vertical induced componentshown respectively at 5605 and 5704 for the high and low inducedvelocity cases, causes the resultant flow angularity to assume aconsiderably more shallow angle in FIG. 56 relative to FIG. 57. Thisbehavior of the flow in the vicinity of the vehicle has the beneficialeffect of reducing the momentum drag component of the overall resistancethat the vehicle experiences as it moves through the air, furtherillustrating the benefits of creation of cruise lift forces on the cabinroof and stabilizer, while off-loading some of the load carried by thefans, possible through the implementation of the provisions shown inFIGS. 43-55. It should be mentioned that the above-mentioned benefitswith respect to streamline geometry and array area applicable also toother center section shapes beside that shown in FIGS. 56 and 57.

While the invention has been described with respect to several preferredembodiments, it will be appreciated that these are set forth merely forpurposes of example, and that many other variations, modifications andapplications of the invention will be apparent.

What is claimed is:
 1. A ducted fan adapted to be mounted in a fuselageof a VTOL vehicle, said ducted fan comprising: at least onelift-producing propeller disposed inside a duct having an inlet and anexit at opposite ends thereof said at least one lift-producing propellermounted for rotation about a duct axis, wherein an arcuately-limitedperipheral sidewall portion of said duct is formed with at least onecontrollable aperture therein, thereby allowing, when the vehicle is inuse and with said controller aperture open, air to flow into an interiorof said duct through both said inlet and said at least one aperture andto flow out of said exit of said duct.
 2. A ducted fan as in claim 1further comprising: a plurality of airfoil-shaped elements disposedwithin said aperture.
 3. A ducted fan as in claim 1 and furthercomprising: a controllably slidable flow blocking element disposed toblock and to permit air flow through said aperture.
 4. The ducted fan ofclaim 1 wherein said aperture extends at least axially downstream ofsaid lift-producing propeller.
 5. The ducted fan of claim 1 wherein saidaperture extends axially upstream and downstream of said at least onelift-producing propeller.
 6. A ducted fan as in claim 1 furthercomprising: a plurality of spaced-apart partition elements disposedwithin said aperture.
 7. A ducted fan as in 6 further comprising: aplurality of externally actuated rotating valves, each valve beingdisposed between two of said partition elements and selectably rotatableto block and to permit air flow around said elements and into said duct.8. A ducted fan as in claim 6 wherein: respective ones of said partitionelements are selectably rotatable to contact a neighboring one of saidpartition elements to block air flow around said elements and into saidduct, and to disengage from said neighboring element to permit air flowaround said elements and into said duct.